Storage arrangement for liquefied gases

ABSTRACT

A membrane tank for liquefied gas storage in which the tank walls are made of relatively narrow vertical strips of thin and flexible sheet material joined to vertical stiffening members which in turn are fastened to an external supporting structure. The vertical stiffening members are alike and each is channel shaped with the web of the channel attached to the supporting member by means of a bolt and slot arrangement which allow vertical thermal expansion. The sheet edges are attached to the legs of the channel members, which are then bent toward each other at the edges and welded together to form lateral expansion joints.

United States Patent Jackson Mar. 14, 1972 [54] STORAGE ARRANGEMENT FOR LIQUEFIED GASES [21 Appl. No.: 76,138

[30] Foreign Application Priority Data Nov. 3, 1969 Great Britain ..53,756/69 [56] References Cited UNITED STATES PATENTS 1,605,513 11/1926 Connery ..52/573 1,973,795 9/1934 Copper, Jr. et al. ..52/573 3,151,416 10/1964 Eakin et al 220/9 LG X 3,203,376 8/1965 Engelhardt.. ..52/573 X 3,243,931 4/1966 Becherer.... .220/9 R X 3,361,284 1/1968 Luka et al.. ..220/9 R 3,406,858 10/1968 Jackson ..220/9 R Primary Examiner-Joseph R. Leclair Assistant Examiner-James R. Garrett Attorney-Max L. Libman ABSTRACT A membrane tank for liquefied gas storage in which the tank walls are made of relatively narrow vertical strips of thin and flexible sheet material joined to vertical stiffening members which in turn are fastened to an external supporting structure. The vertical stifiening members are alike and each is channel shaped with the web of the channel attached to the supporting member by means of a bolt and slot arrangement which allow vertical thermal expansion. The sheet edges are attached to the legs of the channel members, which are then bent toward each other at the edges and welded together to form lateral expansion joints.

11 Claims, 9 Drawing Figures PATENTEDMAR 141912 3,648,879

I nvenlor Roberf G, Jackson PATENTEDMAR 14 191 2 3,648 e79 SHEET 2 I 0F 5 I nventor Robar f G. Jactrfan %W OZ Attorney PATENTEUMAR 14 I972 SHEET 3 [IF 5 Inventor Robe/'7 G, Jbc/(Son 22 #74404 Attorney PATENIEDMAR 14 m2 3. 648 879 saw u 0F 5 I nuentor Robert G ackdon y M 4 Attorney PATENTEDMAR 14- I972 SHEET 5 BF 5 In venlor Roberf' GJbcKaon y %zw 2% A Home y STORAGE ARRANGEMENT FOR LIQUEFIED GASES This invention relates to storage arrangements for liquefied gas and is particularly concerned with storage arrangements of the kind comprising membrane-type tanks, that is to say tanks of thin and flexible sheet material, e.g., metal, which are not subject to cold embrittlement and are not self-supporting but which are supported against internal loads, due to hydrostatic pressure and inertia forces, by surrounding solid insulation.

In this specification the expression liquefied gas means liquid which boils at atmospheric pressure at a temperature below the ambient temperature, for example liquefied natural gas or methane and liquefied petroleum gases such as ethane, propane, butane, ethylene and propylene.

According to this invention in a storage arrangement for liquefied gas of the kind comprising a membrane tank located within a surrounding support structure, the wall of the tank includes vertically extending expansion joints to cater for dimensional changes around the periphery of the tank and vertical stiffening members are spaced around and rigidly attached to the wall of the tank, said stiffening members also being attached to the support structure in such a manner as to permit them and the wall of the tank to move relative to the support structure to cater for any dimensional changes over the height of the tank.

The tank and stiffening members will be made of a material which is ductile at the operating temperature. A suitable material will have a ratio of ultimate tensile strain to thermal strain, over the temperature range to which it may be sub jected, greater than I. By ultimate tensile strain is meant the elongation which the material undergoes before it fails under the effect of a tensile load. By thermal strain is meant the elongation to which the material is subjected if it is restrained from contracting as it cools from ambient temperature to its operating temperature. Since the material cannot be allowed to fail, which could occur at stress concentrations if the ratio was 1, it is preferable that the ratio should be greater than 5. Examples of suitable materials are austenitic stainless steels, 9 percent nickel steel, INVAR (Registered Trademark), aluminum and certain aluminum alloys.

Each stiffening member may be attached to the support structure by means of bolts passing through slots spaced along the stiffening member. Also each stiffening member may be channel shaped, the web being attached to the support structure and the free ends being attached to the wall of the tank; in this case boxes may be secured in a pressuretight manner over each slot and bolt location to provide a secondary line of defense against leakage of the liquefied gas.

At least some of said expansion joints and stiffening members may be coincident so that between them they provide tubular casings which act as expansion joints as well as the means for attachment of the tank to the support structure.

A suitable thermal insulation material may be provided between the support structure and the tank and also within the spaces within the channel-shaped members or tubular casings.

In order that the invention may be readily understood an inground storage arrangement constructed in accordance with the invention and four modifications thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary sectional plan through the wall of the membrane tank and adjacent structure of the first embodiment;

FIG. 2 is an enlarged detail on the line II-II of FIG. 1;

FIG. 3 is an enlarged perspective view of a part of the bottom corner of the membrane tank;

FIG. 4 is a fragmentary diagrammatic plan view of the bottom of the tank;

FIG. 5 is an enlarged perspective view of a part of the bottom of the tank;

FIG. 6 is a detail showing a first modification;

FIG. 7 is a view similar to FIG. 6 showing a second modification;

FIG. 8 is a further view similar to FIG. 6 showing a third modification; and

FIG. 9 is a fragmentary sectional elevation showing a fourth modification.

Referring to FIGS. 1 to 5 of the drawings, the membrane tank is located within a cavity 1 excavated from the surface of the earth. The membrane tank is built up as an assembly from a number of strips 2 of stainless steel which are connected together and extend across the bottom and vertically up the sidewall of the cavity. Each strip 2 is turned over along its longitudinal edges as shown at 3, and each turned-over portion 3 is welded to an edge strip 4, also of stainless steel, which extends along the length of its strip 2. The edge strips 4 lie in a plane transverse to the plane of their respective strips 2. One edge of each edge strip 4 is turned over to provide a portion 5 by which it may be affixed to a suitable support structure carried by the wall of the cavity 1.

The support structure comprises a number of vertical metal beams 6 of Z cross section which are spaced around the cavity adjacent wall thereof and are packed with wet sand 7 which is subsequently frozen to hold the beams 6 firmly in position. The Z-beams 6 provide an inwardly directed face 6a on which the tumedover portions 5 of the edge strips 4 are mounted. Thus to assemble the membrane tank the strips 2 are connected together in side-by-side relationship by welding the turned-over portions 5 of their edge strips 4 together to provide channel-shaped stiffening members, the webs, formed by the turned-over portions 5, of which are slotted along their length as shown at 8 (see FIG. 2) whereby the webs may be attached to the face 6a of an appropriate Z-beam 6, by means of nuts 9. The slots 8 permit relative vertical movement to take place between the wall of the membrane tank and the Z- beams 6 during operation. In order to make the attachment pressuretight a box 11 is placed over each slot and nut, 8 and 9 respectively and is welded to said edge strips 4 and their turned-over portions 5. The other edges 12 of each pair of edge strips 4 joining two adjacent strips 2 are then turned inwardly so that said edges abut and these abutting edges are welded together to provide an expansion joint; each pair of edge strips 4 thus provides a stiffening member and expansion joint in the form of an elongated tubular casing between their respective strips 2.

Conveniently the welding together with the turned-over portions 5 of each pair of edge strips 4 is carried out after these edge strips have been mounted on their respective Z- beams 6 via their turned-over portions 5, in which case, in order to ensure that said turned-over portions 5 are not welded to the faces 6a of these Z-beams, a copper strip may be interposed between said turned-over portions 5 and said faces 6a, or any suitable technique may be employed to ensure that 5 and 6a are not welded together.

The spaces 13 left between the wall of the cavity 1 and the strips 2 are filled with a suitable insulation material, for example polyurethane or PVC foam. The spaces 14 within the tubular casings provided by said pairs of edge strips 4 are also filled with insulation material, which is the same as that used for the spaces 13.

Each strip 2 is bent inwardly at right angles adjacent the bottom of the cavity 1 as are their connecting tubular casings. Alternatively each tubular casing, where it extends round the bottom comer of the tank, may be in two parts, each part extending from the line junction of the corner and a suitably shaped coving may be provided around the bottom corner. The inwardly directed portions of the strips 2 and tubular casings extend radially inwardly over part of the bottom of the cavity 1 and the ends of said strips 2 are turned up to provide an annular flange 15. The central circular space thus left in the bottom of the tank is closed by a disc made up of a further strip and tubular casing assembly, the outer ends of the strips 2 of this assembly also being turned up to provide a further annular flange 16, which is welded onto the flange 15. If necessary, excess metal may be provided for the welded flanges 15, 16 as by making them somewhat wavy in the longitudinal dimension to cater for circumferential contraction of said flanges on cooldown of the storage. The joints between the strips 2 provided by the tubular casings of this disc are staggered with respect to the joints ofthe main wall assembly.

An advantage of the arrangement described above is that the stiffening members for attaching the membrane tank to the Z-beams 6 spaced around the wall of the cavity 1, and the expansion joints for the wall of the tank being coincident with each are integrated to provide a tubular casing.

The insulation layers 13, 14 provide more effective insulation for the membrane tank than the earth alone since this insulation is of the order of 50 times more efficient than the earth and therefore, a much shorter initial cooling-down period is required for the tank prior to it being filled with the liquefied gas.

The particular arrangement described also lends itself to providing evacuated spaces 13 and 14. Thus, this could be achieved for the spaces 13 by coating or providing the face of the cavity 1 with an impervious layer or by providing pairs of spaced strips 2 between the tubular casings. The spaces 14 of course are vacuum-tight providing their ends are suitably sealed. The provision of evacuated spaces for the insulation is described in more detail in U.S. Pat. application Ser. No. 543,726 now U.S. Pat. No. 3,525,661.

It will be appreciated that the wall of the cavity 1 may be faced with a concrete layer in which case the packed wet sand 7 may be dispensed with and the Z-beams 6 set into or onto this layer.

It will also be appreciated that although the embodiment described above is an in-ground storage arrangement, the invention may be used for an aboveground storage arrangement, in which case the structure described will be set into an outer supporting enclosure above ground. In this case the turnedover portions of the edge strips 4 providing the tubular casings may be attached to, for example, hardwood members set in the insulation layers between the inner tank and outer enclosure. This would be preferable to metal members since it would avoid the possibility of hot-cold bridges being formed through the surrounding insulation.

Referring now to FIG. 6 in the first modification the cavity is lines with a layer of concrete 20 and the stiffening members are in the form of preformed channel section members 21 having outwardly turned edge portions 22. Each channel member 21 is rigidly fixed to the concrete layer 20 at spaced positions via suitable bolts 23 screwing into anchoring members 24 set in the concrete layer 20. The edges of the strips 2 are connected together via the portions 22 of the channel members 21. In this modification the expansion joints are again coincident with the stiffening members and are provided by corrugated strips 25 bridging said portions 22, thus forming a tubular casing. As mentioned hereinbefore thermal insulation material 13, 14 may be provided behind strips 2 and within the tubular casings respectively. The corrugation of each expansion strip 25 may be formed with the walls of the corrugation parallel in cross section so that said strip is substantially T- shaped in which case each strip may be welded to the portions 22 of its channel member 21 by the method of our copending U.S. Pat. application No. 121,975 filed Mar. 8, 1971.

Referring to FIG. 7 in the second modification, channel section stiffening members 21 are again provided which are anchored m' the concrete layer 20 via bolts 23 and anchoring members 24 as described with reference to FIG. 6. However, in this modification the outwardly turned portions 22 of the channel members 21 are welded to adjacent strips inwardly of their edges, and the edges are turned away from their channel members 21 and welded together as shown at 26 to provide the expansion joints. In order to reduce the amount of welding on site the strips 2 may be preassembled in pairs via the tubular casings formed by the stiffening members and expansion joints, and holes 27 may be provided in one of the strips of each pair which open into the channel member 21 of the tubular casing at spaced positions corresponding to the spacing of the bolts 23. Each pair of strips 2 may thus be fixed to the concrete layer 20 via the holes 27 and these holes are subsequently sealed by suitable cover plates 28. The free edges of each pair of strips 2 may then be folded and welded to the folded free edge of each adjacent pair of strips 2 as shown at 29 to provide further expansion joints; channel members 21 are not provided at these points and thus, only one tubular casing is provided for each pair of strips 2.

Referring to FIG. 8 this modification is very similar to the modification shown in FIG. 7. The difi'erence is that each channel-shaped stiffening member 21 is preassembled to a single strip 2 intermediate its longitudinal edges and hence is not coincident with an expansion joint. As with FIG. 7 the expansion joints are provided by the longitudinal edges of the strips being folded and welded together.

Referring to FIG. 9, a membrane tank 30 in accordance with this invention is shown located within a cavity of an inground storage arrangement, the stiffening members 31 thereof being anchored to the concrete layer 32 via anchoring members 33. In this arrangement the mouth of the membrane tank is extended and attached to the roof structure via a ring beam 34. The roof structure is described in detail in our copending U.S. Pat. application No. 76,045 filed Sept. 29, 1970. The extended portion 35 comprises a number of membrane strips 36 joined directly at their ends and extending circumferentially around the mouth of the tank with their longitudinal edges 37, 38 being joined to said mouth immediately above the upper ends of the vertical expansion joints 39 and to the ring beam respectively. The strips 36 are provided with corrugations providing horizontally extending expansion joints 40 to cater for any dimensional changes over the height of the tank 30 as a result of temperature variations in use. An insulated ceiling structure 41 is suspended in the tank below the level of the upper ends of the tubular casings 31. This enables the partially open upper ends of the expansion joints 39 to be sealed by suitable cover strips 42 since these will not be required to expand. This is due to the upper ends of the expansion joints not being subjected directly to significant temperature variations in use because of the protection afforded by the ceiling structure 41 and furthermore the level of this ceiling can be adjusted such that these upper ends will not be significantly affected by conduction from the lower parts of the expansion joints.

I claim:

1. a. A storage arrangement for liquefied gas of the kind comprising a membrane tank located within a surrounding support structure,

b. wherein the Wall of the tank includes vertically extending expansion joints to cater for dimensional changes around the periphery of the tank,

c. and vertical stiffening members spaced around and rigidly attached to the wall of the tank,

(1. said stiffening members also being attached to the support structure by expansion means permitting them and the wall of the tank to expand a limited vertical distance relative to the support structure to cater for any dimensional changes over the height of the tank.

. A storage arrangement according to claim 1,

e. wherein the stiffening members hold the wall of the tank spaced from the support structure and the space so formed is filled with a suitable thermal insulation material.

. The storage arrangement according to claim 1,

e. wherein the support structure includes a number of vertical beams to which the stiffening members are attached, said beams being spaced around the support structure at intervals equivalent to the spacing of said stiffening members.

. A storage arrangement according to claim 1,

. wherein at least some of the expansion joints and stiffening members are coincident and shaped so that when welded together between them they provide tubular casings which act as expansion joints as well as the means for attachment of the tank to the support structure.

. A storage arrangement according to claim 4,

f. wherein the spaces within the tubular casings are filled with suitable thermal insulation material.

6. A storage arrangement according to claim 4,

. said expansion means including bolts passing through slots spaced along the stiffening member for attaching each stiffening member to the support structure.

. A storage arrangement according to claim 7, wherein each stiffening member is channel shaped, the

web of the channel being attached to the support structure and the free ends being attached to the wall of the tank.

9. A storage arrangement according to claim 8, g. wherein boxes are secured in a pressuretight manner over each slot and bolt location to provide a secondary line of defense against leakage of the liquefied gas.

10. A storage arrangement according to claim 8, g. including a corrugated strip bridging the free ends of the channel member to provide said expansion joint.

1 l. A storage arrangement according to claim 8, g. wherein said wall of the tank consists of strips of sheet material and a tubular casing is provided by each channel-shaped stiffening member connected to adjacent strips of sheet material inwardly of their cooperating edges,

h. and said cooperating edges are turned away from said stiffening member and connected together to provide an expansion joint for lateral expansion of the wall. 

1. A. A storage arrangement for liquefied gas of the kind comprising a membrane tank located within a surrounding support structure, b. wherein the wall of the tank includes vertically extending expansion joints to cater for dimensional changes around the periphery of the tank, c. and vertical stiffening members spaced around and rigidly attached to the wall of the tank, d. said stiffening members also being attached to the support structure by expansion means permitting them and the wall of the tank to expand a limited vertical distance relative to the support structure to cater for any dimensional changes over the height of the tank.
 2. A storage arrangement according to claim 1, e. wherein the stiffening members hold the wall of the tank spaced from the support structure and the space so formed is filled with a suitable thermal insulation material.
 3. The storage arrangement according to claim 1, e. wherein the support structure includes a number of vertical beams to which the stiffening members are attached, said beams being spaced around the support structure at intervals equivalent to the spacing of said stiffening members.
 4. A storage arrangement according to claim 1, e. wherein at least some of the expansion joints and stiffening members are coincident and shaped so that when welded together between them they provide tubular casings which act as expansion joints as well as the means for attachment of the tank to the support structure.
 5. A storage arrangement according to claim 4, f. wherein the spaces within the tubular casings are filled with suitable thermal insulation material.
 6. A storage arrangement according to claim 4, f. wherein said wall of the tank consists of strips of sheet material, and each tubular casing comprises sidepieces extending in a plane transverse to said strips, g. cooperating edges of said sidepieces being turned over and connected together to provide said stiffening member with a channel shape for connection to the support structure, h. the other cooperating edges of the sidepieces being connected together to provide an expansion joint for lateral expansion of the wall.
 7. A storage arrangement according to claim 1, e. said expansion means including bolts passing through slots spaced along the stiffening member for attaching each stiffening member to the support structure.
 8. A storage arrangement according to claim 7, f. wherein each stiffening member is channel shaped, the web of the channel being attached to the support structure and the free ends being attached to the wall of the tank.
 9. A storage arrangement according to claim 8, g. wherein boxes are secured in a pressuretight manner over each slot and bolt location to provide a secondary line of defense against leakage of the liquefied gas.
 10. A storage arrangement according to claim 8, g. including a corrugated strip bridging the free ends of the channel member to provide said expansion joint.
 11. A storage arrangement according to claim 8, g. wherein said wall of the tank consists of strips of sheet material and a tubular casing is provided by each channel-shaped stiffening member connected to adjacent strips of sheet material inwardly of their cooperating edges, h. and said cooperating edges are turned away from said stiffening member and connected together to provide an expansion joint for lateral expansion of the wall. 